Effect of Alloy Composition on the Glass Forming Ability in Ca-Mg-Zn Alloy System

Abstract:

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The effect of alloy composition on the glass forming ability (GFA) of the Ca-Zn-Mg alloys has been investigated in the present study. The alloy compositions investigated are near Ca-rich ternary eutectic composition; Ca60Mg15Zn25, Ca65Mg10Zn25, Ca65Mg15Zn20, Ca65Mg20Zn15, and Ca70Mg15Zn15. Bulk
metallic glass (BMG) samples with the diameter larger than 5 mm are fabricated by conventional copper mold casting method in air atmosphere. Among the parameters representing the glass forming ability, Trg and γ parameters exhibit good correlation with the maximum diameter of the fully amorphous structure in the alloy compositions investigated in the present study.

Abstract: In this paper, effects of strontium on Mg alloys and preparation technology of Mg-Sr and Mg-Sr-Al master alloys were summarized respectively. Prospects and applications of Sr-Mg master alloys were analyzed too. The results showed that thermodynamics calculation of reaction between SrO and Mg(l) showed that molten Mg can reduce SrO, in which excess of molten. The microstructure of hypoeutectic Mg-Sr binary alloys is composed of primary Mg matrix, and laminary eutectic phase(Mg-Mg17Sr2),but the microstructure of Mg-Sr-Al alloy consists of
plate-like primary Al4Sr, laminary eutectic phase (Mg-Mg17Sr2 or Mg-Mg17Al12 or
Mg-Mg17Sr2-Mg17Al12) embedded in primary dendrites of magnesium matrix. Additive strontium in Mg alloys can refine it grains, reduce degree of porosity, improve mechanical and thermal properties, therefore, Mg-Sr master alloys can be served widely as an additive for modification or as a constituent of Mg alloys, Al alloys, Zn alloys, etc.

Abstract: The electronic structure and phase stability of the Zr-Ni-Al ternary glassy alloys, have
been systematically investigated experimentally and theoretically. Thermal stability and
crystallization process have been clarified by the DSC and XRD measurements. Composition
dependence of the stability parameter; Tg/Tl has been clarified. The electronic structure around the
Fermi level has been investigated by using the high resolution UPS. It is found that there is a
sizable pseudogap at the Fermi level of the electronic structure of the Zr65Ni20Al15 glassy alloy.
The DVXα calculations for the charateristic clusters in the Zr-Ni-Al glassy alloy having high glass
forming ability have been also performed. It is found that these clusters formation reduces the
internal energy and can contribute to the phase stability. The LMTO-ASA band calculations for
the Zr6NiAl2 compound which is the most relevant compound to the Zr60Ni25Al15 glassy alloy have
been also performed. It is found that there is a sizable pseudogap at the Fermi level in its
electronic structure, suggesting exiting of the pseudogap of the glassy alloy.

Abstract: Cast, sub-rapidly solidified and rapidly solidified Al-5Fe alloy and Al-5Fe-3Y alloy were respectively prepared by vacuum melting, suction casting and melt spinning. The effect of increasing cooling rate and adding rare earth Y alloy on microstructures and phase composition were investigated. The results showed that the acicular Al3Fe phase transferred to spherical phase and dispersed secondary precipitations were also found when 3.0 wt% Y was added in the Al-5Fe alloy. Meanwhile, the microstructures were apparently refined by the increasing of cooling rate. The metastable phase A16Fe and intermetallic compound A110Fe2Y phase have been observed in Al-5Fe alloy and Al-5Fe-3Y alloy, respectively.

Abstract: High chromium cast iron alloys are widely used to produce wear resistant components. However, formation of the large carbides restricts their applied range for the components by traditional solidification techniques. The gas atomization is an effective approach to refine their structures, improve their properties and extend their application field. Based on the study of structure evolution of atomized powders of Fe-25Cr-3.9C alloy, this paper investigated the structure evolution of the atomized powders of Fe-25Cr-3.9C alloy with addition of Ni and B elements. It is found that addition of Ni and B elements make more primary lath-shaped phase be formed. As particle size decrease, width of the primary lath-shaped phase gradually decreases, and the structures are all composed of lath-shaped phase in the small powders with diameter less than 38mm. At last, a relative study between two alloys was made, and the structure formation of atomized powders was discussed.

Abstract: Nickel–titanium- group 5A metal (V, Nb, Ta, Zr) alloys are known as promising hydrogen-selective membrane materials. They can potentially be used in membrane reactors, which can produce high-purity H2 and CO2 streams from coal-derived syngas at elevated temperatures. The master alloys were prepared by arc melting using high purity metals in a Ti-gettered argon atmosphere. The alloys were melted several times in order to improve homogeneity. The ingots were induction-melted under a high-purity argon atmosphere in a quartz tube and graphite crucible injected through a nozzle onto a Cu wheel to produce rapidly solidified amorphous ribbons. Thermal stability of the Ni40Ti40Nb20 and Ni32Ti48Nb20 thin tapes has been examined using DTA analysis.